* There are many small holes on the surface of the eggshell, through which air or microorganisms can enter the egg, which will cause deterioration after a long time.
* Air chamber The air chamber is the space formed by cold contraction after the egg is produced. The size of the air chamber can be clearly seen under the light. A small air chamber means that the water in the egg has low volatility and high freshness. On the contrary, the freshness of eggs is poor.
* Egg yolk Egg yolk color is related to food, and the size and hardness of egg yolk are related to feeding methods.
* The water content of concentrated protein is small, and the proportion of concentrated protein in caged eggs is small.
* The protein concentration of leptin is low, the water content is high, and the leptin content of caged eggs is high.
* Yolk band plays the role of fixing yolk. When an egg goes bad or vibrates excessively, it becomes loose. When your ears shake, you can hear noise.
* The small white spots on the yolk of the ovule become embryos after fertilization.
The quality of yolk and protein is the main factor that determines the taste of eggs. Indexes that determine the quality of egg yolk and protein.
1. 1 yolk quality and yolk index
Egg yolk color is one of the important indexes affecting the quality of poultry eggs. Under natural conditions, the darker the yolk color, the better the quality of eggs and the higher the nutritional value. The greater the proportion of egg yolk, the better the taste and the richer the nutrition. The dry matter of egg yolk is positively correlated with the weight of egg yolk. Using the ratio of yolk weight to yolk weight as a selection trait can not only increase the dry matter yield, but also increase the yolk weight. So it can be changed by breeding. Egg yolk quality is usually expressed by egg yolk index. When determining the yolk index, beat the egg on the glass plate, measure the yolk height (IIun) and yolk diameter (mm), and take the height/diameter×10 as the yolk index. The yolk index of fresh eggs on that day was 0.38%~0.49%.
1.2. protein quality and protein index.
Protein quality is an important material basis of egg freshness, which is measured by protein height, Hartmann unit and protein pH value. The higher the height of protein, the fresher the eggs, but the height of protein is related to the size of eggs. Therefore, Hash units are used to measure the freshness of eggs. The higher the Hartmann unit, the better the protein viscosity and the higher the protein quality. The quality grading standards are: Haas unit of AA > 72, Hartmann unit of A > 60-72, Hartmann unit of B.
Second, the factors that determine the taste of eggs
1. Genetic factors
The egg yolk specific gravity and protein index of different varieties are different, and the taste of eggs is also different due to genetic factors.
2. Feed factors
There are many kinds of raw materials for protein feed and chicken feed, some are used to provide energy, and some are used to provide protein. The source of fishy smell is protein. In order to save costs, some feed enterprises and farms feed chickens with some cheap things, including some spoiled fish meal, bone meal, rapeseed meal and cottonseed meal. It is these "bad elements" that make eggs smell fishy. Include many feed materials, which can be transferred to eggs through absorption and metabolism. Therefore, good feed formula and feed raw materials are a major factor in determining the taste of eggs.
3. Physiological factors
Generally speaking, the eggs laid by chickens in the peak period taste better than those laid in the later period.
4. Disease factors
If laying hens are infected with some diseases during laying, such as viral high fever and follicular degeneration caused by thin egg white, for example, eggs infected with reproductive branches during laying are not only poor in eggshell quality, but also deformed eggs with one side up and thin egg white, which will inevitably affect the taste of eggs. In addition, the intestinal diseases of chickens affect the absorption of nutrients, which will also cause problems in the taste of eggs, especially the "fishy smell" of eggs laid by chickens during the period of infection with ring-dead enteritis and coccidiosis will increase; When a chicken gets salpingitis, the taste of the eggs produced will also get worse.
5. Storage and transportation of eggs
5. 1 temperature and humidity problems. The optimum storage conditions of eggs are 10-2 1℃ and the relative humidity is 70-80%. American experts are studying the influence of egg temperature on egg products, and the data conclusions are shown in the following table.